Preparation process for producing liquid fertilizer from methionine waste liquid and application of liquid fertilizer

Abstract

The invention discloses a preparation process for producing a liquid fertilizer from methionine waste liquid and application of the liquid fertilizer, and relates to the technical field of fertilizer preparation, and the preparation process has the advantages that efficient and specific adsorption of methionine is realized by preparing a specific adsorption material, and the organic ligand 2, 5-dimercapto-1, 3, 4-thiadiazole of a thioether functional group can be used for preparing the liquid fertilizer. The 1, 4-phthalic acid can synthesize a metal organic framework (MOF) material with metal ions and zinc ions, a thioether functional group can generate strong interaction with sulfur atoms in methionine, methionine is efficiently recognized and combined, the surface of the MOF is uniformly covered with a polymer coating, and through interaction with carboxyl and amino in methionine, the methionine can be efficiently recognized. According to the present invention, the methionine can be accurately separated from the complex methionine fermentation waste liquid, the polystyrene-imidazole copolymer can achieve the structure stabilizing and adsorption performance enhancing effects in the coating, and the obtained material has the stable methionine specific adsorption function, and can be repeatedly used, such that the production cost is reduced, and the production efficiency is improved. And the recovery efficiency of methionine is obviously improved.

Description

Technical Field

[0001] The invention relates to the technical field of fertilizer preparation, in particular to a preparation process for producing liquid fertilizer from methionine waste liquid and application thereof. Background Art

[0002] In the field of modern industry and agriculture, the effective utilization of resources and environmental protection are crucial issues. As an important nutrient, methionine is widely used in many industries such as feed and medicine. However, a large amount of fermentation waste liquid will be generated in the production process of methionine. If these waste liquids are not properly treated, they will bring a series of problems. With the continuous development of the methionine industry, its production scale has gradually expanded, and the corresponding waste liquid output has also continued to increase. The traditional waste liquid treatment method is often simple and extensive, which not only wastes a lot of resources, but also discards the underutilized methionine and valuable metal ions such as iron, zinc, and copper, and causes serious pollution to the environment. The existing technology has certain defects. First, the existing technology lacks efficient and specific adsorption materials to efficiently recover methionine in methionine fermentation waste liquid, resulting in low recovery efficiency, high cost and susceptibility to interference from impurities. Secondly, the existing technology is difficult to achieve classified recovery of different components when treating waste liquid, and the resource utilization rate is low and it is easy to pollute the environment. Furthermore, the existing technology cannot effectively utilize waste liquid resources to prepare stable compound fertilizers, which wastes resources and lacks sustainable fertilizer sources. For this reason, we propose a preparation process for producing liquid fertilizer from methionine waste liquid and its application. Summary of the invention

[0003] The purpose of the present invention is to provide a preparation process for producing liquid fertilizer from methionine waste liquid and its application.

[0004] In order to solve the problems raised in the above background technology, the present invention provides the following technical solution: a preparation process for producing liquid fertilizer from methionine waste liquid, the preparation process for producing liquid fertilizer comprising the following specific steps: Step 1, preparing a specific adsorption material, selecting an organic ligand containing a thioether functional group, 2,5-dimercapto-1,4-phthalic acid, and a metal ion, zinc ion, to synthesize a metal organic framework (MOF) material, dissolving 2,5-dimercapto-1,4-phthalic acid and zinc nitrate in N,N-dimethylformamide (DMF) for stirring reaction, centrifuging after the reaction and washing with deionized water, and drying after washing to obtain a MOF material having a sulfur-containing ligand, then preparing a polymer coating solution containing an imidazole group, dissolving a polystyrene-imidazole copolymer in dichloromethane to form a uniform solution, and then immersing the synthesized MOF material in the polymer coating solution for stirring reaction, so that the polymer coating is evenly covered on the MOF surface, filtering, washing and drying after the reaction is completed to obtain a material having a specific methionine adsorption function; Step 2: adsorbing methionine, contacting the methionine fermentation waste liquid with the prepared specific adsorption material for adsorption reaction. During this process, the sulfur-containing ligands in the material, the sulfur atoms in the polymer coating and the imidazole groups interact with the sulfur atoms, carboxyl groups and amino groups in methionine to achieve specific adsorption of methionine, while other substances in the waste liquid are not adsorbed. After the adsorption is completed, a filtering operation is performed to separate the remaining waste liquid and the adsorption material after the adsorption of methionine, and the adsorption material is transferred to a desorption container for desorption reaction. Hydrochloric acid solution is used as a desorbent. During the desorption process, hydrochloric acid reacts with the methionine adsorbed on the material to separate the methionine from the adsorption material, completing the methionine recovery and collecting the remaining waste liquid; Step 3, extracting useful components from the remaining waste liquid, slowly adding sodium hydroxide solution to the remaining waste liquid, stirring and mixing it after the addition is completed, so that the iron ions, zinc ions and copper ions in the waste liquid form hydroxide precipitates, and the precipitate is allowed to stand after the stirring is completed. Then, the precipitate is filtered out through a filter, and the precipitate is washed with deionized water to remove impurities, and then the remaining waste liquid is poured into a separation funnel and ethyl acetate is added. After fully stirring and mixing, it is allowed to stand for a period of time to allow the solution to stratify, and then the stopcock of the separation funnel is slowly opened to release the aqueous phase waste liquid of the lower layer, and the ethyl acetate layer of the upper layer is collected, thereby achieving separation and collection of organic matter; Step 4: extracting the iron, zinc and copper metal ions in the ethyl acetate layer, and then mixing and stirring these metal ions with terephthalic acid containing carboxyl and hydroxyl functional groups as organic ligands in a solvent N,N-dimethylacetamide to react. After the reaction is completed, a preliminary metal organic framework structure is initially formed. Then, the adsorbed methionine is introduced into the reaction system for reaction, so that the methionine interacts with the metal organic framework to form a methionine-metal organic framework complex; Step 5: prepare liquid fertilizer by mixing the methionine-metal organic framework complex with urea as a nitrogen source, potassium dihydrogen phosphate as a phosphorus source, and potassium nitrate as a potassium source, then adding water as a solvent, and then adding humic acid as an additive and stirring to react, and obtaining liquid fertilizer after the reaction is completed.

[0005] As a further scheme of the present invention: In the step 1, the preparation of the MOF material containing sulfur ligands is specifically as follows: 8 mol / L-12 mol / L of 2,5-dimercapto-1,4-phthalic acid and 10 mol / L-15 mol / L of zinc nitrate are dissolved in N,N-dimethylformamide (DMF), and the mixture is stirred at 75°C-85°C for 10h-15h. After the stirring reaction, the mixture is centrifuged at a speed of 3000r / min-3500r / min for 15min-20min. After centrifugation, the mixture is washed three times with deionized water and then dried at 60°C-70°C for 8h-10h.

[0006] As a further scheme of the present invention: in the step 1, when preparing the polymer coating solution containing imidazole groups, the mass fraction of the polystyrene-imidazole copolymer is 15%-25%, and the stirring reaction is stirred at 35°C-45°C for 5h-8h. After the reaction is completed, the material is filtered using a microporous filter membrane with a pore size of 0.2μm-0.4μm. After filtration, the material is washed with dichloromethane 1-3 times and dried at 45°C-55°C for 5h-8h.

[0007] As a further scheme of the present invention: in the step 2, the adsorption reaction is stirred for 3h-5h at a temperature of 20℃-30℃ and a stirring speed of 150r / min-200r / min. After the adsorption is completed, the filtration uses a microporous filter membrane with a pore size of 0.1μm-0.2μm, the concentration of the hydrochloric acid solution of the desorbent is 0.5mol / L-1mol / L, and the desorbent is added in a ratio of 1:5-8 to the mass ratio of the adsorbent material to the desorbent. The desorption reaction is carried out at a temperature of 40℃-50℃ and a stirring speed of 100r / min-150r / min for desorption for 2h-3h.

[0008] As a further scheme of the present invention: in the step three, the concentration of the sodium hydroxide solution is 1.5mol / L-2.5mol / L, the stirring reaction of the remaining waste liquid and the sodium hydroxide solution is controlled to have a stirring speed of 180r / min-220r / min, and the stirring is carried out for 20min-30min. After the stirring is completed, the precipitate is allowed to stand for 1.5h-2.5h, and then the precipitate is washed 2-4 times with deionized water. The volume ratio of the added ethyl acetate to the waste liquid is 0.8-1.2:1, and after adding ethyl acetate and stirring and mixing, it is necessary to stand for 1.5h-2.5h to allow the solution to stratify.

[0009] As a further scheme of the present invention: in the step 4, the process of extracting the iron, zinc and copper metal ions in the ethyl acetate layer is as follows: a dilute sulfuric acid solution with a concentration of 1 mol / L-2 mol / L is added to ethyl acetate at a mass ratio of 1:3-5, and the reaction is stirred at a temperature of 40°C-50°C and a stirring speed of 150r / min-200r / min for 1h-2h to allow the metal ions to precipitate and dissolve in the dilute sulfuric acid, and then, insoluble impurities are removed by filtration to obtain a solution containing iron, zinc and copper metal ions, and the solution is evaporated and concentrated, and the solution volume is concentrated to 1 / 3-1 / 2 of the original volume at a temperature of 60°C-80°C, and finally, it is cooled to room temperature to allow the metal ions to precipitate in the form of crystals, and the crystals are collected by filtration to obtain the desired iron, zinc, copper and other metal ions.

[0010] As a further scheme of the present invention: in the step 4, the concentration of the organic ligand terephthalic acid in the stirring reaction is 8 mol / L-12 mol / L, the mixed stirring reaction is carried out at 95°C-105°C and a stirring speed of 250r / min-350r / min for 8h-12h, the ratio of the amount of methionine added to the total mass of the reaction system is 1:2-3, the reaction temperature for adding methionine is 55°C-65°C, the pH value is 6.5-7.5, and the reaction time is 6h-10h.

[0011] As a further scheme of the present invention: in the step five, the mass ratio of the added complex, urea, potassium dihydrogen phosphate and potassium nitrate is 1:1.5-2.5:0.8-1.2:0.8-1.2, the added amount of solvent water is 30%-50% of the total mass of the mixture, the added amount of additive humic acid is 2%-5% of the total mass of the mixture, the stirring reaction is controlled at a stirring speed of 130r / min-170r / min, heated to 45°C-55°C and reacted for 5h-8h.

[0012] In addition, the present invention also provides an application of methionine waste liquid to produce liquid fertilizer, and the liquid fertilizer is applied in agricultural planting to provide nutrition for crops through drip irrigation and sprinkler irrigation.

[0013] By adopting the above technical solution, compared with the prior art, the beneficial effects of the present invention are: 1. The present invention realizes efficient and specific adsorption of methionine by preparing a specific adsorption material. The organic ligand 2,5-dimercapto-1,4-phthalic acid of the thioether functional group can synthesize a metal organic framework (MOF) material with metal ions and zinc ions. The thioether functional group can produce a strong interaction with the sulfur atom in methionine, efficiently identify and bind methionine, and the prepared polymer coating is evenly covered on the surface of the MOF. The imidazole group further enhances the adsorption capacity of methionine, interacts with the carboxyl and amino groups in methionine, and accurately separates methionine from the complex methionine fermentation waste liquid, reducing the interference of impurities in the waste liquid. The polystyrene-imidazole copolymer plays a role in stabilizing the structure and enhancing the adsorption performance in the coating, ensuring the efficiency and reliability of the adsorption process. Through a series of operations such as centrifugation, washing, and drying, the obtained material has a stable and specific methionine adsorption function and can be reused, thereby reducing the production cost and significantly improving the recovery efficiency of methionine. 2. The present invention adds sodium hydroxide solution to the remaining waste liquid. This operation prompts the metal ions such as iron, zinc, copper, etc. in the waste liquid to form a stable hydroxide precipitate. The sodium hydroxide solution changes the existence form of the metal ions by chemically reacting with the metal ions, so that the metal ions are converted from a soluble state to an insoluble precipitate. For the extraction of organic matter, ethyl acetate is used to separate the organic matter by layers by utilizing the characteristics that ethyl acetate is immiscible with water and has a density less than that of water. As an excellent organic solvent, ethyl acetate can effectively dissolve the organic matter in the waste liquid. After sufficient stirring and mixing, due to the density difference, the ethyl acetate layer containing the organic matter is naturally located in the upper layer, thereby achieving clear separation of the organic matter and the aqueous phase waste liquid. The ethyl acetate layer containing the organic matter is successfully collected. This process not only achieves the classified recovery of different components in the waste liquid, greatly improves the utilization rate of resources, but also reduces the pollution of the waste liquid to the environment, and avoids the random discharge of harmful substances in the waste liquid. 3. The present invention further processes the extracted metal ion precipitate to obtain pure metal ions such as iron, zinc, and copper, and dissolves the metal ion precipitate in the dilute sulfuric acid by adding a dilute sulfuric acid solution. The dilute sulfuric acid reacts chemically with the metal ion precipitate to release the metal ions into the solution again. Then, the metal ions are mixed with terephthalic acid containing carboxyl and hydroxyl functional groups in a specific solvent. The metal ions and organic ligands react in a specific ratio and at a certain temperature and stirring speed to form a stable metal organic framework structure. The carboxyl and hydroxyl functional groups can coordinate with the metal ions to construct a framework with a specific spatial structure. Then, the adsorbed methionine is introduced, and the sulfur atoms, carboxyl groups, amino groups and other functional groups in the methionine interact with the metal organic framework to form a methionine-metal organic framework complex. This complex combines the nutritional properties of methionine and the stability of the metal organic framework, and provides a key composite component for the subsequent preparation of liquid fertilizers, which not only improves the recycling value of resources, but also converts waste liquid resources that may have been discarded into valuable products, thereby providing an efficient and sustainable fertilizer source for agricultural production. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of the process steps in an embodiment of the present invention; Figure 2 It is a schematic diagram comparing the performance parameters of the embodiment and the comparative example in the embodiment of the present invention. DETAILED DESCRIPTION

[0015] The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention.

[0016] In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0017] Please see attached Figure 1 -Attached Figure 2 The present invention provides a preparation process for producing liquid fertilizer from methionine waste liquid, and the preparation process for producing liquid fertilizer comprises the following specific steps: Step 1, preparing a specific adsorption material, selecting an organic ligand containing a thioether functional group, 2,5-dimercapto-1,4-phthalic acid, and a metal ion, zinc ion, to synthesize a metal organic framework (MOF) material, dissolving 2,5-dimercapto-1,4-phthalic acid and zinc nitrate in N,N-dimethylformamide (DMF) for stirring reaction, centrifuging after the reaction and washing with deionized water, and drying after washing to obtain a MOF material having a sulfur-containing ligand, then preparing a polymer coating solution containing an imidazole group, dissolving a polystyrene-imidazole copolymer in dichloromethane to form a uniform solution, and then immersing the synthesized MOF material in the polymer coating solution for stirring reaction, so that the polymer coating is evenly covered on the MOF surface, filtering, washing and drying after the reaction is completed to obtain a material having a specific methionine adsorption function; Step 2: adsorbing methionine, contacting the methionine fermentation waste liquid with the prepared specific adsorption material for adsorption reaction. During this process, the sulfur-containing ligands in the material, the sulfur atoms in the polymer coating and the imidazole groups interact with the sulfur atoms, carboxyl groups and amino groups in methionine to achieve specific adsorption of methionine, while other substances in the waste liquid are not adsorbed. After the adsorption is completed, a filtering operation is performed to separate the remaining waste liquid and the adsorption material after the adsorption of methionine, and the adsorption material is transferred to a desorption container for desorption reaction. Hydrochloric acid solution is used as a desorbent. During the desorption process, hydrochloric acid reacts with the methionine adsorbed on the material to separate the methionine from the adsorption material, completing the methionine recovery and collecting the remaining waste liquid; Step 3, extracting useful components from the remaining waste liquid, slowly adding sodium hydroxide solution to the remaining waste liquid, stirring and mixing it after the addition is completed, so that the iron ions, zinc ions and copper ions in the waste liquid form hydroxide precipitates, and the precipitate is allowed to stand after the stirring is completed. Then, the precipitate is filtered out through a filter, and the precipitate is washed with deionized water to remove impurities, and then the remaining waste liquid is poured into a separation funnel and ethyl acetate is added. After fully stirring and mixing, it is allowed to stand for a period of time to allow the solution to stratify, and then the stopcock of the separation funnel is slowly opened to release the aqueous phase waste liquid of the lower layer, and the ethyl acetate layer of the upper layer is collected, thereby achieving separation and collection of organic matter; Step 4: extracting the iron, zinc and copper metal ions in the ethyl acetate layer, and then mixing and stirring these metal ions with terephthalic acid containing carboxyl and hydroxyl functional groups as organic ligands in a solvent N,N-dimethylacetamide to react. After the reaction is completed, a preliminary metal organic framework structure is initially formed. Then, the adsorbed methionine is introduced into the reaction system for reaction, so that the methionine interacts with the metal organic framework to form a methionine-metal organic framework complex; Step 5: prepare liquid fertilizer by mixing the methionine-metal organic framework complex with urea as a nitrogen source, potassium dihydrogen phosphate as a phosphorus source, and potassium nitrate as a potassium source, then adding water as a solvent, and then adding humic acid as an additive and stirring to react, and obtaining liquid fertilizer after the reaction is completed.

[0018] In one embodiment of the present invention: In step one, the preparation of the MOF material containing sulfur ligand is as follows: 8 mol / L-12 mol / L of 2,5-dimercapto-1,4-phthalic acid and 10 mol / L-15 mol / L of zinc nitrate are dissolved in N,N-dimethylformamide (DMF), and the reaction is stirred at 75°C-85°C for 10h-15h. After the stirring reaction, centrifugation is performed with a control speed of 3000r / min-3500r / min for 15min-20min. After centrifugation, the mixture is washed 3 times with deionized water and then dried at 60°C-70°C for 8h-10h.

[0019] In one embodiment of the present invention: in step 1, when preparing a polymer coating solution containing imidazole groups, the mass fraction of the polystyrene-imidazole copolymer is 15%-25%, and the stirring reaction is stirred at 35°C-45°C for 5h-8h. After the reaction is completed, the material is filtered using a microporous filter membrane with a pore size of 0.2μm-0.4μm. After filtration, the material is washed with dichloromethane 1-3 times and dried at 45°C-55°C for 5h-8h.

[0020] In one embodiment of the present invention: in step 2, the adsorption reaction is stirred for 3h-5h at a temperature of 20°C-30°C and a stirring speed of 150r / min-200r / min. After the adsorption is completed, filtration is performed using a microporous filter membrane with a pore size of 0.1μm-0.2μm, and the concentration of the hydrochloric acid solution of the desorbent is 0.5mol / L-1mol / L. The desorbent is added at a mass ratio of 1:5-8 between the adsorbent material and the desorbent. The desorption reaction is carried out at a temperature of 40°C-50°C and a stirring speed of 100r / min-150r / min for 2h-3h.

[0021] In one embodiment of the present invention: in step three, the concentration of the sodium hydroxide solution is 1.5mol / L-2.5mol / L, the stirring reaction of the remaining waste liquid and the sodium hydroxide solution is controlled at a stirring speed of 180r / min-220r / min, and the stirring is performed for 20min-30min. After the stirring is completed, the precipitate is allowed to stand for 1.5h-2.5h, and then the precipitate is washed 2-4 times with deionized water. The volume ratio of the added ethyl acetate to the waste liquid is 0.8-1.2:1, and after adding ethyl acetate and stirring and mixing, it is necessary to stand for 1.5h-2.5h to allow the solution to stratify.

[0022] In one embodiment of the present invention: in step 4, the process of extracting the iron, zinc and copper metal ions in the ethyl acetate layer is as follows: a dilute sulfuric acid solution with a concentration of 1 mol / L-2 mol / L is added to ethyl acetate at a mass ratio of 1:3-5, and the reaction is stirred at a temperature of 40°C-50°C and a stirring speed of 150r / min-200r / min for 1h-2h to allow the metal ions to precipitate and dissolve in the dilute sulfuric acid, and then, insoluble impurities are removed by filtration to obtain a solution containing iron, zinc and copper metal ions, and the solution is evaporated and concentrated at a temperature of 60°C-80°C to concentrate the solution volume to 1 / 3-1 / 2 of the original volume, and finally, cooled to room temperature to allow the metal ions to precipitate in the form of crystals, and the crystals are collected by filtration to obtain the desired iron, zinc, copper and other metal ions.

[0023] In one embodiment of the present invention: in step 4, the concentration of the organic ligand terephthalic acid in the stirring reaction is 8 mol / L-12 mol / L, the mixed stirring reaction is carried out at 95°C-105°C and a stirring speed of 250r / min-350r / min for 8h-12h, the ratio of the amount of methionine added to the total mass of the reaction system is 1:2-3, the reaction temperature for adding methionine is 55°C-65°C, the pH value is 6.5-7.5, and the reaction time is 6h-10h.

[0024] In one embodiment of the present invention: in step five, the mass ratio of the added complex, urea, potassium dihydrogen phosphate and potassium nitrate is 1:1.5-2.5:0.8-1.2:0.8-1.2, the amount of solvent water added is 30%-50% of the total mass of the mixture, the amount of additive humic acid added is 2%-5% of the total mass of the mixture, the stirring reaction is controlled at a stirring speed of 130r / min-170r / min, heated to 45°C-55°C and reacted for 5h-8h.

[0025] In one embodiment of the present invention: in step one, the prepared material with the function of specifically adsorbing methionine is subjected to surface activation treatment, specifically, the material is immersed in a solution containing a surfactant, the surfactant is sodium dodecyl sulfate, the concentration is 5 mol / L-8 mol / L, the immersion time is 3h-5h, and the temperature is 30°C-40°C. After the surface activation treatment, the material's adsorption capacity for methionine is further improved, and the adsorption rate is also significantly accelerated, thereby enhancing the efficiency and effect of the entire preparation process in the methionine adsorption link.

[0026] In one embodiment of the present invention: in step 2, after the desorption is completed, the desorbent hydrochloric acid solution is recovered and processed, and a specific ion exchange resin is used to pass the hydrochloric acid solution through a resin column, so that the hydrochloric acid and the resin undergo an ion exchange reaction and are adsorbed on the resin. When the resin is saturated with adsorption, a sodium hydroxide solution with a concentration of 2mol / L-3mol / L is used for elution to obtain a regenerated hydrochloric acid solution, which can be used again in the desorption process. This not only reduces pollution to the environment, but also reduces production costs and improves resource utilization.

[0027] In one embodiment of the present invention: in step 4, after extracting the metal ions in the ethyl acetate layer, the obtained solution containing iron, zinc and copper metal ions is pretreated, and an appropriate amount of complexing agent is added to the solution, the complexing agent is disodium ethylenediaminetetraacetic acid, and the concentration is 3 mol / L-5 mol / L. The solution is stirred and reacted at a temperature of 45°C-55°C for 1h-2h. The complexing agent can form a stable complex with the metal ions to prevent the metal ions from precipitating or other adverse reactions in subsequent reactions, thereby improving the stability and formation efficiency of the metal organic framework structure.

[0028] In one embodiment of the present invention: in step five, when preparing liquid fertilizer, a new type of synergist is added to the mixture, the synergist is seaweed extract, and the addition amount is 1%-3% of the total mass of the mixture. The seaweed extract is rich in natural active substances, including growth hormones and trace elements, which can promote the absorption and utilization of nutrients in the liquid fertilizer by plants, improve the fertilizer efficiency of the liquid fertilizer, and also enhance the environmental protection and sustainability of the liquid fertilizer.

[0029] Example 1, please refer to the attached Figure 1 -Attached Figure 2First, a specific adsorption material was prepared. 12 mol / L of 2,5-dimercapto-1,4-phthalic acid and 15 mol / L of zinc nitrate were dissolved in N,N-dimethylformamide (DMF). The mixture was stirred at 85°C for 15 h. After the stirring reaction, the mixture was centrifuged at a speed of 3500 r / min for 20 min. After centrifugation, the mixture was washed three times with deionized water and then dried at 70°C for 10 h to obtain a MOF material with sulfur-containing ligands. Next, a polymer coating solution containing imidazole groups was prepared. A polystyrene-imidazole copolymer with a mass fraction of 25% was dissolved in dichloromethane to form a uniform solution. liquid, then, the synthesized MOF material was immersed in the polymer coating solution and stirred at 45°C for 8 hours to make the polymer coating evenly cover the MOF surface. After the reaction was completed, the material was filtered using a microporous filter membrane with a pore size of 0.4μm. After filtration, the material was washed with dichloromethane three times and dried at 55°C for 8 hours to obtain a material with the function of specific adsorption of methionine. Secondly, methionine adsorption was performed. The methionine fermentation waste liquid and the prepared specific adsorption material were stirred and reacted at a temperature of 30°C and a stirring speed of 200r / min for 5 hours. During this process, the sulfur-containing ligands in the material and the sulfur in the polymer coating The atoms and imidazole groups interact with the sulfur atoms, carboxyl groups and amino groups in methionine to achieve specific adsorption of methionine, while other substances in the waste liquid are not adsorbed. After the adsorption is completed, a microporous filter membrane with a pore size of 0.2 μm is used for filtration to separate the remaining waste liquid and the adsorption material after the adsorption of methionine. The adsorption material is transferred to a desorption container, and a hydrochloric acid solution with a concentration of 1 mol / L is used as a desorbent. The desorbent is added in a ratio of 1:8 to the mass ratio of the adsorbent to the desorbent. The desorption is stirred at a temperature of 50°C and a stirring speed of 150 r / min for 3 hours to separate methionine from the adsorption material. The remaining waste liquid was collected and recovered as methionine. Then, the useful components in the remaining waste liquid were extracted. A sodium hydroxide solution with a concentration of 2.5 mol / L was slowly added to the remaining waste liquid. After the addition was completed, the solution was stirred at a stirring speed of 220 r / min for 30 min to form hydroxide precipitates of the iron ions, zinc ions and copper ions in the waste liquid. After the stirring was completed, the precipitate was allowed to stand for 2.5 h. Then, the precipitate was filtered out through a filter and washed with deionized water for 4 times to remove impurities. Then, the remaining waste liquid was poured into a separation funnel and ethyl acetate was added in a volume ratio of 1.2:1 to the waste liquid. After sufficient stirring and mixing, the mixture was allowed to stand for 2.5h to allow the solution to separate, then slowly open the stopcock of the separation funnel, release the lower aqueous phase waste liquid, collect the upper ethyl acetate layer, thereby achieving separation and collection of organic matter, then extract the iron, zinc, and copper metal ions in the ethyl acetate layer, add a 2 mol / L dilute sulfuric acid solution to the ethyl acetate at a mass ratio of 1:5, stir and react at a temperature of 50°C and a stirring speed of 200r / min for 2h, so that the metal ions are precipitated and dissolved in the dilute sulfuric acid, then filter and remove insoluble impurities to obtain a solution containing iron, zinc, and copper metal ions, evaporate and concentrate the solution, and concentrate the solution volume to 1 / 2 of the original volume at a temperature of 80°C, finally, cool to room temperature to allow the metal ions to precipitate in the form of crystals, collect the crystals by filtration, and obtain the desired iron, zinc, copper and other metal ions, then, mix these metal ions with 12 mol / L terephthalic acid containing carboxyl and hydroxyl functional groups as The organic ligands were mixed in the solvent N,N-dimethylacetamide, and reacted at 105°C and a stirring speed of 350r / min for 12h. After the reaction was completed, a preliminary metal organic framework structure was initially formed. Then, the adsorbed methionine was introduced into the reaction system, and the ratio of the amount of methionine added to the total mass of the reaction system was 1:3. Under the conditions of a temperature of 65°C, a pH value of 7.5, and a reaction time of 10h, methionine interacted with the metal organic framework to form a methionine-metal organic framework complex. Finally, liquid fertilizer was prepared by mixing the methionine-metal organic framework complex with nitrogen source urea, phosphorus source potassium dihydrogen phosphate, and potassium source potassium nitrate in a mass ratio of 1:2.5:1.2:1.2, and then adding 50% of the total mass of the mixture as a solvent, and then adding 5% of the total mass of the mixture as an additive. Humic acid was added as an additive, and the mixture was stirred at a speed of 170r / min, heated to 55°C, and reacted for 8h to obtain liquid fertilizer. .

[0030] Comparative Example 1, please refer to the attached Figure 1 -Attached Figure 2First, a specific adsorption material was prepared. 8 mol / L of 2,5-dimercapto-1,4-phthalic acid and 10 mol / L of zinc nitrate were dissolved in N,N-dimethylformamide (DMF). The mixture was stirred at 75°C for 10 h. After the stirring reaction, the mixture was centrifuged at a speed of 3000 r / min for 15 min. After centrifugation, the mixture was washed with deionized water three times and then dried at 60°C for 8 h to obtain a MOF material with sulfur-containing ligands. Next, a polymer coating solution containing imidazole groups was prepared. A polystyrene-imidazole copolymer with a mass fraction of 15% was dissolved in dichloromethane to form a uniform solution. Then, the synthesized MOF material was immersed in the polymer coating solution and stirred at 35°C for 5 hours to make the polymer coating evenly cover the MOF surface. After the reaction was completed, the material was filtered using a microporous filter membrane with a pore size of 0.2μm. After filtration, the material was washed once with dichloromethane and dried at 45°C for 5 hours to obtain a material with the function of specific adsorption of methionine. Secondly, methionine adsorption was carried out. The methionine fermentation waste liquid was stirred with the prepared specific adsorption material at a temperature of 20°C and a stirring speed of 150r / min for 3 hours. During this process, the sulfur-containing ligands in the material and the sulfur atoms in the polymer coating The imidazole group interacts with the sulfur atom, carboxyl group and amino group in methionine to achieve specific adsorption of methionine, while other substances in the waste liquid are not adsorbed. After the adsorption is completed, a microporous filter membrane with a pore size of 0.1 μm is used for filtration to separate the remaining waste liquid and the adsorption material after the adsorption of methionine. The adsorption material is transferred to a desorption container, and a hydrochloric acid solution with a concentration of 0.5 mol / L is used as a desorbent. The desorbent is added in a ratio of 1:5 to the mass ratio of the adsorbent material to the desorbent. The desorption is carried out at a temperature of 40°C and a stirring speed of 100 r / min for 2 hours to separate methionine from the adsorption material. The remaining waste liquid was collected and recovered as methionine. Then, the useful components in the remaining waste liquid were extracted. A sodium hydroxide solution with a concentration of 1.5 mol / L was slowly added to the remaining waste liquid. After the addition was completed, the stirring speed was 180 r / min and stirred for 20 min to make the iron ions, zinc ions and copper ions in the waste liquid form hydroxide precipitation. After the stirring was completed, the precipitation was allowed to stand for 1.5 h. Then, the precipitation was filtered out through a filter and washed twice with deionized water to remove impurities. Then, the remaining waste liquid was poured into a separation funnel and ethyl acetate was added in a volume ratio of 0.8:1 to the waste liquid. After sufficient stirring and mixing, it was allowed to stand for 1.5h to allow the solution to separate, then slowly open the stopcock of the separation funnel, release the aqueous phase waste liquid in the lower layer, collect the ethyl acetate layer on the upper layer, thereby achieving separation and collection of organic matter, then extract the iron, zinc, and copper metal ions in the ethyl acetate layer, add a 1 mol / L dilute sulfuric acid solution to the ethyl acetate at a mass ratio of 1:3, stir and react at a temperature of 40°C and a stirring speed of 150r / min for 1h, so that the metal ions are precipitated and dissolved in the dilute sulfuric acid, then filter and remove insoluble impurities to obtain a solution containing iron, zinc, and copper metal ions, evaporate and concentrate the solution, and concentrate the solution volume to 1 / 3 of the original volume at a temperature of 60°C, finally, cool to room temperature to allow the metal ions to precipitate in the form of crystals, collect the crystals by filtration, and obtain the desired iron, zinc, copper and other metal ions, then, react these metal ions with 8 mol / L terephthalic acid containing carboxyl and hydroxyl functional groups The organic ligand is mixed in the solvent N,N-dimethylacetamide, and the reaction is carried out at 95°C and a stirring speed of 250r / min for 8h. After the reaction is completed, a preliminary metal organic framework structure is initially formed. Then, the adsorbed methionine is introduced into the reaction system, and the ratio of the amount of methionine added to the total mass of the reaction system is 1:2. Under the conditions of a temperature of 55°C, a pH value of 6.5, and a reaction time of 6h, methionine interacts with the metal organic framework to form a methionine-metal organic framework complex. Finally, liquid fertilizer is prepared by mixing the methionine-metal organic framework complex with nitrogen source urea, phosphorus source potassium dihydrogen phosphate, and potassium source potassium nitrate in a mass ratio of 1:1.5:0.8:0.8, and then adding 30% of the total mass of the mixture as a solvent, and then adding 2% of the total mass of the mixture as an additive. Humic acid is added as an additive, and the stirring speed is 130r / min, heated to 45°C and reacted for 5h to obtain liquid fertilizer. .

[0031] Comparative Example 2, please refer to the attached Figure 1 -Attached Figure 2First, a specific adsorption material was prepared. 14 mol / L of 2,5-dimercapto-1,4-phthalic acid and 17 mol / L of zinc nitrate were dissolved in N,N-dimethylformamide (DMF). The mixture was stirred at 60°C for 15 h. After the stirring reaction, the mixture was centrifuged at a speed of 3500 r / min for 20 min. After centrifugation, the mixture was washed three times with deionized water and then dried at 70°C for 10 h to obtain a MOF material with sulfur-containing ligands. Next, a polymer coating solution containing imidazole groups was prepared. A polystyrene-imidazole copolymer with a mass fraction of 28% was dissolved in dichloromethane to form a uniform solution. liquid, then, the synthesized MOF material was immersed in the polymer coating solution and stirred at 45°C for 8 hours to make the polymer coating evenly cover the MOF surface. After the reaction was completed, the material was filtered using a microporous filter membrane with a pore size of 0.4μm. After filtration, the material was washed with dichloromethane three times and dried at 55°C for 8 hours to obtain a material with the function of specific adsorption of methionine. Secondly, methionine adsorption was performed. The methionine fermentation waste liquid and the prepared specific adsorption material were stirred and reacted at a temperature of 30°C and a stirring speed of 200r / min for 5 hours. During this process, the sulfur-containing ligands in the material and the sulfur in the polymer coating The atoms and imidazole groups interact with the sulfur atoms, carboxyl groups and amino groups in methionine to achieve specific adsorption of methionine, while other substances in the waste liquid are not adsorbed. After the adsorption is completed, a microporous filter membrane with a pore size of 0.2 μm is used for filtration to separate the remaining waste liquid and the adsorption material after the adsorption of methionine. The adsorption material is transferred to a desorption container, and a hydrochloric acid solution with a concentration of 1 mol / L is used as a desorbent. The desorbent is added in a ratio of 1:5 to the mass ratio of the adsorbent to the desorbent. The desorption is carried out at a temperature of 50°C and a stirring speed of 150 r / min for 3 hours to separate methionine from the adsorption material. The remaining waste liquid was collected and recovered into methionine. Then, the useful components in the remaining waste liquid were extracted. A sodium hydroxide solution with a concentration of 1.5 mol / L was slowly added to the remaining waste liquid. After the addition was completed, the stirring speed was 220 r / min and stirred for 30 minutes to make the iron ions, zinc ions and copper ions in the waste liquid form hydroxide precipitation. After the stirring was completed, the precipitation was allowed to stand for 2.5 hours. Then, the precipitation was filtered out through a filter and washed with deionized water for 4 times to remove impurities. Then, the remaining waste liquid was poured into a separation funnel and ethyl acetate was added in a volume ratio of 1.2:1 to the waste liquid. After sufficient stirring and mixing, it was allowed to stand for 2.5h to allow the solution to separate, then slowly open the stopcock of the separation funnel, release the lower aqueous phase waste liquid, collect the upper ethyl acetate layer, thereby achieving separation and collection of organic matter, then extract the iron, zinc, and copper metal ions in the ethyl acetate layer, add a 3 mol / L dilute sulfuric acid solution to the ethyl acetate at a mass ratio of 1:3, stir and react at a temperature of 50°C and a stirring speed of 200r / min for 2h, so that the metal ions are precipitated and dissolved in the dilute sulfuric acid, then filter to remove insoluble impurities, and obtain a solution containing iron, zinc, and copper metal ions, evaporate and concentrate the solution, and concentrate the solution volume to 1 / 5 of the original volume at a temperature of 80°C, finally, cool to room temperature, so that the metal ions precipitate in the form of crystals, collect the crystals by filtration, and obtain the desired iron, zinc, copper and other metal ions, then, mix these metal ions with 12 mol / L terephthalic acid containing carboxyl and hydroxyl functional groups as The organic ligands were mixed in the solvent N,N-dimethylacetamide, and reacted at 105°C and a stirring speed of 350r / min for 12h. After the reaction was completed, a preliminary metal organic framework structure was initially formed. Then, the adsorbed methionine was introduced into the reaction system, and the ratio of the amount of methionine added to the total mass of the reaction system was 1:3. Under the conditions of temperature of 65°C, pH value of 7.0, and reaction time of 10h, methionine interacted with the metal organic framework to form a methionine-metal organic framework complex. Finally, liquid fertilizer was prepared by mixing the methionine-metal organic framework complex with nitrogen source urea, phosphorus source potassium dihydrogen phosphate, and potassium source potassium nitrate in a mass ratio of 1:2.5:1.2:1.2, and then adding 50% of the total mass of the mixture as a solvent, and then adding 2% of the total mass of the mixture as an additive. Humic acid was added at a stirring speed of 170r / min, heated to 55°C and reacted for 8h to obtain liquid fertilizer. .

[0032] Comparative Example 3, please refer to the attached Figure 1 -Attached Figure 2First, a specific adsorption material was prepared. 10 mol / L 3-mercaptopropionic acid and 12 mol / L zinc chloride were dissolved in dimethyl sulfoxide (DMSO), and the mixture was stirred at 80°C for 12 h. After the stirring reaction, the mixture was centrifuged at a speed of 3200 r / min for 18 min. After centrifugation, the mixture was washed with deionized water for 3 times and then dried at 65°C for 9 h to obtain a MOF-like material with sulfur-containing ligands. Next, a polyvinylamine coating solution containing amino groups was prepared. Polyvinylamine with a mass fraction of 20% was dissolved in chloroform to form a uniform solution. Then, the synthesized MOF-like material was immersed in the polyvinylamine coating solution and stirred at 40°C for 7 h to allow the polymer coating to form a uniform solution. The layer is evenly covered on the surface of MOF. After the reaction is completed, the material is filtered using a microporous filter membrane with a pore size of 0.3μm. After filtration, the material is washed twice with chloroform and dried at 50°C for 7h to obtain a material with a certain methionine adsorption function. Secondly, methionine adsorption is carried out. The methionine fermentation waste liquid is stirred with the prepared specific adsorption material at a temperature of 28°C and a stirring speed of 180r / min for 4h. During this process, the sulfur-containing ligands in the material and the amino groups in the polymer coating interact with the sulfur atoms, carboxyl groups and amino groups in methionine to achieve the adsorption of methionine. After the adsorption is completed, it is filtered using a microporous filter membrane with a pore size of 0.15μm to separate the methionine adsorbed The remaining waste liquid and adsorbent material are transferred to a desorption container, and a sulfuric acid solution with a concentration of 0.8 mol / L is used as a desorbent. The desorbent is added in a ratio of 1:7 according to the mass ratio of the adsorbent to the desorbent. The desorption is carried out at a temperature of 45°C and a stirring speed of 130 r / min for 2.5 hours to separate methionine from the adsorbent material, complete methionine recovery and collect the remaining waste liquid. Then, the useful components in the remaining waste liquid are extracted, and a potassium hydroxide solution with a concentration of 2 mol / L is slowly added to the remaining waste liquid. After the addition is completed, the stirring speed is 200 r / min and stirred for 25 minutes to form hydroxide precipitation of iron ions, zinc ions and copper ions in the waste liquid. After the stirring is completed, the precipitate is allowed to stand for 2 hours. Then, the precipitate is filtered out through a filter and washed with deionized water for 3 times to remove impurities. Then, the remaining waste liquid is poured into a separation funnel and propyl acetate is added in a volume ratio of 1:1 to the waste liquid. After sufficient stirring and mixing, the solution is allowed to stand for 2 hours to separate. Then, the stopcock of the separation funnel is slowly opened to discharge the aqueous phase waste liquid at the lower layer and collect the propyl acetate layer at the upper layer, thereby achieving the separation and collection of organic matter. Then, the iron, zinc and copper metal ions in the propyl acetate layer are extracted, and a dilute hydrochloric acid solution with a concentration of 1.5 mol / L is added to the propyl acetate at a mass ratio of 1:4. The reaction is stirred at a temperature of 45°C and a stirring speed of 180 r / min for 1.5h, the metal ions are precipitated and dissolved in dilute hydrochloric acid, then the insoluble impurities are filtered to obtain a solution containing iron, zinc and copper metal ions, the solution is evaporated and concentrated, and the solution volume is concentrated to 1 / 3 of the original at a temperature of 70°C. Finally, it is cooled to room temperature to precipitate the metal ions in the form of crystals, and the crystals are collected by filtration to obtain the required iron, zinc, copper and other metal ions. Then, these metal ions are mixed with benzoic acid containing a carboxyl functional group at a concentration of 10 mol / L as an organic ligand in a solvent of N-methylpyrrolidone, and the reaction is carried out at 100°C and a stirring speed of 300r / min for 10h. After the reaction is completed, a preliminary metal organic framework structure is initially formed, and then Then, the adsorbed methionine was introduced into the reaction system, and the ratio of the amount of methionine added to the total mass of the reaction system was 1:2.5. Under the conditions of temperature of 60°C, pH value of 7, and reaction time of 8h, methionine interacted with the metal organic framework to form a methionine-metal organic framework complex. Finally, liquid fertilizer was prepared by mixing the methionine-metal organic framework complex with nitrogen source ammonium chloride, phosphorus source potassium monohydrogen phosphate, and potassium source potassium sulfate in a mass ratio of 1:2:1:1, and then adding 45% of water as a solvent, and then adding 4% of fulvic acid as an additive, and stirring at a speed of 160r / min, heating to 50°C and reacting for 7h to obtain liquid fertilizer. .

[0033] Experimental design Experimental materials and equipment: multiple batches of waste liquid from the same source of methionine fermentation waste liquid, 2,5-dimercapto-1,4-phthalic acid, zinc nitrate, N,N-dimethylformamide (DMF), polystyrene-imidazole copolymer, dichloromethane, hydrochloric acid solution, sodium hydroxide solution, ethyl acetate, dilute sulfuric acid solution, terephthalic acid containing carboxyl and hydroxyl functional groups, nitrogen source urea, phosphorus source potassium dihydrogen phosphate, potassium source potassium nitrate, humic acid, 3-mercaptopropionic acid, zinc chloride, dimethyl sulfoxide (DMSO), etc. Experimental equipment: agitator, centrifuge, filter, separation funnel, heating equipment, atomic absorption spectrometer, high performance liquid chromatograph, etc. Experimental steps: Take multiple batches of methionine fermentation waste liquid from the same source, ensure that the volume and composition of each batch of waste liquid are relatively stable, and calibrate and debug the experimental instruments; Experimental operation stage: according to the process steps of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3, the operations were performed respectively, and each experimental group was repeated 5 times to ensure the reliability of the results; (1) Methionine adsorption step Before adsorption, the initial methionine content (unit: g / L) in each batch of wastewater was determined using HPLC; The adsorption operation was performed according to the respective processes, and after the adsorption was completed, the methionine content in the remaining waste liquid was determined again using a high performance liquid chromatograph; The calculation formula of methionine recovery efficiency is: methionine recovery efficiency = (initial methionine content - methionine content in the remaining waste liquid) / initial methionine content × 100%.

[0034] (2) Steps for extracting useful components from the remaining waste liquid For metal ion precipitation, after filtration and washing, use an electronic balance to accurately weigh the mass of the metal ion precipitate (unit: g); For the extraction of organic matter, the collected organic matter layer is evaporated and dried, and then the mass of the dried organic matter is weighed using an electronic balance, which is the amount of organic matter extracted (unit: g).

[0035] (3) After preparing liquid fertilizer Determination of nitrogen content in liquid fertilizer: The Kjeldahl method is used to determine the nitrogen content in liquid fertilizer. The specific operation is to take a certain amount of liquid fertilizer sample, add concentrated sulfuric acid and a catalyst for digestion, convert organic nitrogen into ammonium nitrogen, and then determine the nitrogen content (unit: g / L) through distillation, titration and other steps; Conduct a liquid fertilizer stability test, place the prepared liquid fertilizer in an environment with a temperature of 25°C and a relative humidity of 50%, observe and record the time for unstable phenomena such as stratification and precipitation to occur, and use this as a measure of the liquid fertilizer stability (unit: day); Data recording and analysis phase Record the data obtained by each experimental group in each step in detail in a table; Conduct statistical analysis on experimental data, such as calculating mean values, standard deviations, etc., to assess the reliability and accuracy of experimental results; By comparing the differences in methionine recovery efficiency, metal ion precipitation quality, organic matter extraction, liquid fertilizer nutrient content and liquid fertilizer stability among the experimental groups, it is concluded that Example 1 is the best in terms of beneficial effects.

[0036] As attached Figure 2 As shown, by comparing the differences in methionine recovery efficiency, metal ion precipitation quality, organic matter extraction, liquid fertilizer nutrient content and liquid fertilizer stability among the experimental groups, it is concluded that Example 1 is the best in preparing liquid fertilizer.

[0037] Although the present invention is disclosed as above in terms of preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A process for producing liquid fertilizer from methionine waste liquid, characterized in that: The preparation process for producing liquid fertilizer comprises the following specific steps: Step 1, preparing a specific adsorption material, selecting an organic ligand containing a thioether functional group, 2,5-dimercapto-1,4-phthalic acid, and a metal ion, zinc ion, to synthesize a metal organic framework (MOF) material, dissolving 2,5-dimercapto-1,4-phthalic acid and zinc nitrate in N,N-dimethylformamide (DMF) for stirring reaction, centrifuging after the reaction and washing with deionized water, and drying after washing to obtain a MOF material having a sulfur-containing ligand, then preparing a polymer coating solution containing an imidazole group, dissolving a polystyrene-imidazole copolymer in dichloromethane, and then immersing the synthesized MOF material in the polymer coating solution for stirring reaction, so that the polymer coating is evenly covered on the MOF surface, filtering, washing and drying after the reaction is completed to obtain a material having a specific methionine adsorption function; Step 2: adsorbing methionine, contacting the methionine fermentation waste liquid with the prepared specific adsorption material for adsorption reaction, filtering to separate the remaining waste liquid and the adsorption material after the adsorption of methionine, transferring the adsorption material to a desorption container for desorption reaction, using hydrochloric acid solution as a desorbent, completing methionine recovery and collecting the remaining waste liquid; Step 3, extracting useful components from the remaining waste liquid, slowly adding sodium hydroxide solution to the remaining waste liquid, stirring and mixing it after the addition is completed, letting the precipitate stand after the stirring is completed, then filtering the precipitate through a filter, and washing the precipitate with deionized water, then pouring the remaining waste liquid into a separation funnel, adding ethyl acetate, stirring and mixing it thoroughly, and letting it stand for a period of time to allow the solution to stratify, then slowly opening the stopcock of the separation funnel, releasing the aqueous phase waste liquid at the lower layer, and collecting the ethyl acetate layer at the upper layer, thereby achieving separation and collection of organic matter; Step 4: extracting the iron, zinc and copper metal ions in the ethyl acetate layer, and then mixing these metal ions with terephthalic acid containing carboxyl and hydroxyl functional groups as organic ligands in a solvent N,N-dimethylacetamide for reaction, and then introducing the adsorbed methionine into the reaction system for reaction to form a methionine-metal organic framework complex; Step 5: prepare liquid fertilizer by mixing the methionine-metal organic framework complex with urea as a nitrogen source, potassium dihydrogen phosphate as a phosphorus source, and potassium nitrate as a potassium source, then adding water as a solvent, and then adding humic acid as an additive and stirring to react, and obtaining liquid fertilizer after the reaction is completed.

2. A process for producing liquid fertilizer from methionine waste liquid according to claim 1, characterized in that: In the step 1, the preparation of the MOF material containing sulfur ligand is specifically as follows: 8 mol / L-12 mol / L of 2,5-dimercapto-1,4-phthalic acid and 10 mol / L-15 mol / L of zinc nitrate are dissolved in N,N-dimethylformamide (DMF), and the mixture is stirred at 75°C-85°C for 10h-15h. After the stirring reaction, the mixture is centrifuged at a speed of 3000r / min-3500r / min for 15min-20min. After centrifugation, the mixture is washed with deionized water for 3 times, and then dried at 60°C-70°C for 8h-10h.

3. A process for producing liquid fertilizer from methionine waste liquid according to claim 1, characterized in that: In the step 1, when preparing the polymer coating solution containing imidazole groups, the mass fraction of the polystyrene-imidazole copolymer is 15%-25%, and the stirring reaction is stirred at 35° C.-45° C. for 5 h-8 h. After the reaction is completed, the material is filtered using a microporous filter membrane with a pore size of 0.2 μm-0.4 μm. After filtration, the material is washed with dichloromethane 1 to 3 times and dried at 45° C.-55° C. for 5 h-8 h.

4. A process for producing liquid fertilizer from methionine waste liquid according to claim 1, characterized in that: In the step 2, the adsorption reaction is stirred for 3h-5h at a temperature of 20°C-30°C and a stirring speed of 150r / min-200r / min. After the adsorption is completed, the filtration uses a microporous filter membrane with a pore size of 0.1μm-0.2μm, the concentration of the hydrochloric acid solution of the desorbent is 0.5mol / L-1mol / L, and the desorbent is added at a mass ratio of 1:5-8 between the adsorbent material and the desorbent. The desorption reaction is stirred at a temperature of 40°C-50°C and a stirring speed of 100r / min-150r / min for desorption for 2h-3h.

5. A process for producing liquid fertilizer from methionine waste liquid according to claim 1, characterized in that: In the step 3, the concentration of the sodium hydroxide solution is 1.5mol / L-2.5mol / L, the stirring reaction of the remaining waste liquid and the sodium hydroxide solution is controlled to have a stirring speed of 180r / min-220r / min, and the stirring is performed for 20min-30min. After the stirring is completed, the precipitate is allowed to stand for 1.5h-2.5h, and then the precipitate is washed 2-4 times with deionized water. The volume ratio of the added ethyl acetate to the waste liquid is 0.8-1.2:1, and after the ethyl acetate is added and stirred and mixed, it is necessary to stand for 1.5h-2.5h to allow the solution to stratify.

6. A process for producing liquid fertilizer from methionine waste liquid according to claim 1, characterized in that: In the step 4, the process of extracting the iron, zinc and copper metal ions in the ethyl acetate layer is as follows: a dilute sulfuric acid solution with a concentration of 1 mol / L-2 mol / L is added to ethyl acetate at a mass ratio of 1:3-5, and the reaction is stirred at a temperature of 40°C-50°C and a stirring speed of 150r / min-200r / min for 1h-2h to allow the metal ions to precipitate and dissolve in the dilute sulfuric acid, and then, insoluble impurities are removed by filtration to obtain a solution containing iron, zinc and copper metal ions, and the solution is evaporated and concentrated, and the solution volume is concentrated to 1 / 3-1 / 2 of the original volume at a temperature of 60°C-80°C, and finally, it is cooled to room temperature to allow the metal ions to precipitate in the form of crystals, and the crystals are collected by filtration to obtain the desired iron, zinc, copper and other metal ions.

7. A process for producing liquid fertilizer from methionine waste liquid according to claim 1, characterized in that: In the step 4, the concentration of the organic ligand terephthalic acid in the stirring reaction is 8 mol / L-12 mol / L, the mixed stirring reaction is carried out at 95°C-105°C and a stirring speed of 250r / min-350r / min for 8h-12h, the ratio of the amount of methionine added to the total mass of the reaction system is 1:2-3, the reaction temperature for adding methionine is 55°C-65°C, the pH value is 6.5-7.5, and the reaction time is 6h-10h.

8. A process for producing liquid fertilizer from methionine waste liquid according to claim 1, characterized in that: In the step 5, the mass ratio of the added complex, urea, potassium dihydrogen phosphate and potassium nitrate is 1:1.5-2.5:0.8-1.2:0.8-1.2, the amount of solvent water added is 30%-50% of the total mass of the mixture, the amount of additive humic acid added is 2%-5% of the total mass of the mixture, the stirring reaction is controlled at a stirring speed of 130r / min-170r / min, heated to 45°C-55°C and reacted for 5h-8h.

9. An application of methionine waste liquid to produce liquid fertilizer, which is applicable to the preparation process of methionine waste liquid to produce liquid fertilizer according to any one of claims 1 to 8, characterized in that: The liquid fertilizer is used in agricultural planting to provide nutrition for crops through drip irrigation and sprinkler irrigation.

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